The object of the project is the analysis of the cortex of primitive mammals in the hope of discovering the common elements of mammalian cortical organization and its evolutionary modifications into the anthropoid form. Toward this end we perform ablation-behavior experiments on animals selected on the basis of their recency of common ancestry with anthropoids, namely, opossums, hedgehogs, tree shrews, bushbabies and monkeys, as well as more usual laboratory animals such as cats or rats. These ablation-behavior experiments have focused on first one then another cortical area beginning first with the primary sensory areas then progressing to secondary sensory or association areas and contribution of sensory and association cortex to neurological and psychological adjustment of man to his environment.